Gas discharge device



p 1953 L. R. LANDREY ETAL ,65 ,510

GAS DISCHARGE DEVICE Filed Oct. 3, 1951 INVE NTOR LEO R LANDREY Y ALFRED MAZZEI CURRENT /w/gy 50 /00 /50 200 250 300 350 400 450 ATTORNE Patented Sept. 15, 1953 GAS DISCHARGE DEVICE Leo Raymond Landrey,

Mazzei, Richmond Hil mesne assignments, t America as represent Lynbrook, and Alfred l, N. Y., assignors, by the United States of ed by the United States Atomic Energy Commission Application October 3, 1951, Serial N 0. 249,554

Claims.

The present invention relates to electron discharge tubes and more particularly to cold cathode gas-filled electron discharge devices, particularly adapted for voltage regulator operation.

An object of the present invention is the provision of a gas-filled voltage regulator tube adapted for stable operation at low current values.

Another object of the present invention is to improve the uniformity of operation of voltage regulator devices.

Still another object of the present invention is to increase the reliability, at low operating currents, operation of voltage regulator devices.

Still another object of the present invention is to facilitate the manufacture of cold cathode gas filled discharge devices.

The foregoing objects and others which may appear from the following detailed description are attained in accordance with an aspect of the present invention by providing a cold cathode gas-filled electron discharge device having a uniformly processed cathode surface, of an area no larger than that which will be wholly covered by the glow discharge at the maximum rated current so that the discharge is prevented from shifting about over the cathode surface to seek out the most active part of the cathode surface. The variations in activity of different cathode spots tended, in prior art tubes of which we are aware, to cause changes in cathode potential drop with each shift.

Other aspects of the present invention provide for means for adequately degassing and processing such a limited cathode surface by providing auxiliary heating means within the gas filled envelope in thermal conducting relationship with the cathode so that the cathode can be adequately heated.

A more complete understanding of the present invention will be had by reference to the following detailed description which is accompanied by a drawing in which:

Fig. 1 is a transverse sectional view of an embodiment of the present invention taken along line l--l of Figure 2, while;

Fig. 2 is a longitudinal section of the tube shown in Figure 1.

Fig. 3 is a view similar to Figure 1 but illustrating a modification of the present invention, while;

Fig. 4 is a longitudinal cross-section of the embodiment of Figure 3, and;

Fig. 5 is a chart of a group of curves diagram- 2 matically illustrating some of the operating principles of the invention.

The structures shown in Figures 1 and 2 includes a hermetically sealed vitreous envelope Ill closed at one end by a glass header l2 through which a number of lead-in conductors it pass and closed at the other end by a seal-01f tip I6 through which a lead-in conductor I8 is sealed.

The tube is provided witha pair of internal spacer discs or wafers '20 and 22 of insulating material such as mica. 22 support in proper relative position an anode 24 and a cathode 26. Anode 24 comprises a metal plate, preferably corrugated to increase its rigidity, welded to an extension of lead-in wire I8 which passes through appropriate apertures in spacer discs 20 and 22. comprises a small L-shaped wire or rod welded or otherwise secured to a supporting plate 28. Plate 23 is corrugated similarly to anode plate 24 and is similarly held in position between spacer washers 20 and 22 by an extension of lead-in conductor l4 passing through appropriate apertures in discs 20 and 22 and welded or otherwise secured to the plate 28.

Auxiliary mounting tabs at each end of plates 24 and. 28 passing through spacers 20 and 22 may be provided if desired but are not here shown as being necessary to an understanding of the present invention. In order to maintain the proper spacing between header l2 and the lower insulating spacer 22, a number of dummy conductors 30 may be sealed into header I2 of such length and so disposed as to bear against the lower surface of spacer '22 and prevent it from tipping or shifting in position. The cathode rod is preferably constructed of pure nickel and the end facing anode 24 is ground and polished so that it is smooth and flat. Cathode supporting plate 28 is preferably constructed of metal having a higher work function than nickel, or if constructed of nickel or steel, may be carbonized or painted with a colloidal suspension of graphite in order to provide a surface with an effective high work function.

Metals other than nickel which may be used for j cathode supporting plate 23 and which may not require coating with colloidal graphite or carbonizing are platinum, gold, arsenic and osmium. Either a solid metal or a thin plating over a baser metal may be employed.

Anode 24 may be constructed of nickel. It is provided with a getter capsule 32 welded or otherwise secured to the rear-surface of anode 24 with respect to the cathode so directed that The spacer discs 20 and Cathode 26 3 as the getter is flashed the material vaporized from the getter is deposited on the glass wall of the tube away from the active discharge area of the tube.

The envelope I is filled with a helium-argon gas mixture at a lowpressure. Duerto the small effective areaof cathode 26, that represented by the polished end of the L-shaped wire, substantially all of the glow discharge taking place in. the tube during operation takes placebetween the end of the cathode rod 26 and anode'24'. The cathode spot substantially entirely-'cove1s1the: end of the cathode rod at the rated maxiinum current of the tube and is effectively prevented from Wandering about over-the surface of-"the cathode rod or progressing to the cathode supporting plate, since for the cathode-spot-to move: away from the end of rod 26 the ionization path must increase substantially. Furthermoreif overload should cause thexdischarge to move to platee2812itxvill notremain theretexcept at grossly excessive values of current because of: the effective high. work; function; of. the surface of plate 28. This construction should be contrasted with previously known apparently similar. structureswhich are designedrto use a.pointed' rod-:onlyxfor starting and have thelargecathode area activated by the useof' metalhaving. a low-'work function;

Tubes constructed: according to the embodiment' describeduabove and utilizing a cathode rod 0.15 inch. in: diameter havemaintained a rated voltage of 150 volts plus or minus 1 /2 volts overthe major part: of? the microainpere range for long periods of? time I without: change.

Figs.- 3' -and l illustrating. a=. modified" form of the invention use the same reference character forthe same parts. This embodiment obtains the restricted area ofi cathode over which the dischargemay be supported by utilizing a straight cathode rod Ml' supported between insulating spacers-20 and ZZ spaced apart such distance asto-provide asdesired clear areaof'the cathode-rod between the spacers. In this form of construe: tion-"theanodeis likewise a straight wire 42 passingthrough appropriate aligned apert'ures in the spacers 20 and 22. In order to prevent adischarge from-taking place between the anode andcathode outside of the space between the spacers,

ceramicsleeves -dl and $3 are secured respectively over the cathode'lead-in wire [4-, the anode leadin' wire Idadjacent'spacer disc Zllland over the portion of anode rod 42" which extends beneath spacer disc-Z2 In thisform of construction the getter: 32' is support'ed by a U-shaped loop ofwir-e M'se'cured'to a dumm lead lfi molded into glass header [2'' and passing through spacer discs 20' and 22.- Wi're-46isswaged into wing-like formationsbel'ow spacer 22 asshownat tl and abovespacer 20: or: short pieces of tubing welded in place at those locations in order to supportthe" discs intheir: proper spaced relationship. The getter is:prefer-ably so arranged as todirect' the getter flash"; toward the glass wall of envelope I0 and away from the mica 20 to prevent the possibility of any contamination of the spacer 20 reducing the insulation between; the anode memher andthe cathode member.

In -order to provide a const'ant source of ionization within the'tube so that'st'arting conditions are maintained uniform after long periods of inactivity anactivation primer 50 maybe inserted in the-tube. A radio active material, such. as. cobalt G0 has been. found satisfactory.

It will benoted that the structureshown in;

Figures 3 and 4 utilizes the principle of restricted area of the cathode for improved regulation in the same way as the embodiment shown in Figures 1 and 2. The form of construction used in Figures 3 and 4 is somewhat easier to fabricate than that shown in Figures 1- and :2, but due to the absence of the-cathode. heating plate 28 of the first modification, more care is required in processing the tube during the exhaust and filling of theenvelope with the gas in order to obtain maximum-life and stability.

Thedotted-line curve A in Fig. 5, illustrates a typical voltage-current characteristic of cold cathode gas-filledregulator tubes and is plotted withreference to-the upper scales of milliamperes. It will benoted that no regulation is normally. obtained-between point D, the breakdown voltage of the tube, and point E, the first knee on thecurve. The position of point E along the regulation curve is governed by the size of the cathode. The'larger the cathode area the higher theminimum value of current at which regulationibegins. The. substantially horizontal line portion of curve. A between point E and point. F is the region of normal operation. Point F' is reached'when the entire cathode area is covered by glow. An abnormal glow with failure of regulation takes place beyond point F at about 30' milliamperescurrent and as'the current is further increased the tube eventuallybreaks down into an arc-discharge at point G. gas-filled voltage regulator tubes of which we are aware, point E on. the curve isreached at a current value of somewhere near 5 milliamperes andnoreliable regulating. action can be obtained at lesser values of current. However it is often necessary to provide regulated sources of voltage in situationswhere a current drain of- 5' milliamperes would be grossly excessive.

The regulating characteristic of tubes constructed according to our invention is shown by the solid line curve B'of Figure 5'. By reference tothe lower scale o'f currents in microamperes in Figure 5, it: will be noted: that only minor vari ations inthe regulated voltagetake place in the region fromito- 150 microamperes and thereafter substantially no variations in voltage take place over; a: comparatively wide range of variation of. current drain.

While We havev shown and particularly described several modifications of our invention it should be clearly. understood that our invention s notlimited'thereto butthat modifications within. the scope of the appended claims may be made.

What we claim is:

1; A- gas discharge voltage. regulator tube including within a hermetically sealed envelope containing an ionizable gas, an anode and a cathode, said. cathode having an effective area no greater than that of the glow which the tube mustsupport at maximum rated current.

2. A gas dischargedevice at set forth in claim 1, wherein the effective area of. the cathode isrestricted by covering areas of said cathode with a material which will not support cathode activity.

3; A gas discharge device as set forth in claim 1', wherein the effective area of the cathode is restricted by covering areasof said cathode with a ceramic insulating material.

4. A gas discharge device as set forth in claim 1, wherein the effective area of thecathode is restricted by covering areas of'said cathode with material-:havinga high work function.

In most normal 5. A gas regulator tube as set forth in claim 1, wherein said cathode is constituted of a section of wire having a polished end surface directed toward said anode.

6. A gas regulator tube as set forth in claim 1, wherein said cathode is constituted of a section of wire having a polished end surface directed toward said anode and supported on a metallic plate so treated as to inhibit cathode activity.

7. A gas regulator tube as set forth in claim 1, wherein said cathode is constituted of an L- shaped section of wire supported on a plate spaced from said anode and having a polished end surface directed towards said anode.

8. A gas discharge voltage regulator tube including Within a hermetically sealed envelope containing an ionizable gas, a rod-like anode and a rod-like cathode each passing through a pair of spaced insulating discs so spaced that said cathode has an effective area no greater than that of the glow which the tube must support with maximum rated current.

9. A gas discharge device as set forth in claim 8, wherein the portions of said anode and cathode outwardly of said spacers are treated to inhibit a gas discharge therebetween.

10. A gas discharge device as set forth in claim 8, a radio active material is attached to one of said discs to facilitate initiation of gas discharge between said cathode and anode.

LEO RAYMOND LANDREY. ALFRED MAZZEI.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,905,153 Cloud Apr. 25, 1933 2,416,285 Buckingham et a1. Feb. 25, 1947 2,504,581 Power Apr. 18, 1950 

